This application proposes studies of the local metabolic effects of various general anesthetics on rat spinal cord. The metabolic response of the cord and supraspinal somatosensory relay structures to high-intensity electrical stimulation of the sciatic nerve during anesthesia will also be examined. The quantitative, autoradiographic 2-(14C)deoxyglucose technique for measuring local glucose utilization will be applied to male Sprague-Dawley rats. Animal preparation is to include femoral artery and vein catheters, a tracheostomy, artificial ventilation and, where appropriate, dissection of the sciatic nerve for subsequent stimulation. Arterial blood gases and pH, blood pressure, rectal temperature and hematocrit will also be measured. In the studies of anesthesia alone, morphine (5 mg/kg) and pentobarbital (15 mg/kg) will be administered intravenously; 70% nitrous oxide or 1.2% halothane will be delivered by inhalation. Animals in which the effect of stimulation (1msec, 10 Hz, voltage 5 x's threshold) during anesthesia is to be studied will receive graded morphine or halothane anesthesia. The autoradiographs produced by the 2-(14C)DG method will be analyzed with either a manual densitometer or a computerized image-processing system. Glucose utilization of the lumbar spinal cord will be measured in two areas of dorsal horn and in the ventral horn; numerous brain regions will be measured. From the optical density measurements, the plasma data, knowledge of various constants and the mathematical model of the method, values for local glucose utilization will be calculated. Neurophysiological data suggest that anesthetics have lamina-specific actions in the spinal cord. In addition, anesthetics block evoked neuronal activity in specific supraspinal somatosensory relay structures. Inasmuch as functional activity and metabolic rate are closely coupled in the nervous system, selective metabolic effects might therefore be expected. The effect of anesthesia on spinal cord metabolism may have implications for studies of cord trauma since changes in metabolic rate produced by the drugs could alter the cord response to injury. The degree to which metabolism increases during stimulation and anesthesia could be important for clinical situations in which substrate supply is inadequate to meet the increased metabolic demand.